The present invention relates generally to apparatus for use in constructing permanent structures, such as homes, buildings and the like, and more particularly, to a new and improved form means for forming pre-cast structural members.
In general, the exterior walls of permanent structures intended for providing shelter, such as houses, and apartment or office buildings should satisfy several criteria. They must be structurally sound and provide thermal insulation for the occupants. They should also be resistant to fire, water damage, termites, etc., and should be durable and easily maintainable. In addition, the methods for constructing such exterior walls should be inexpensive in both labor and materials required, and should enable flexibility in design for an attractive and appealing exterior facade. Moreover, the materials utilized should cause little or no ecological waste or destruction.
In general, however, current construction techniques fail to satisfy at least ome of these criteria, while no such technique has heretofore satisfied all such criteria. As presently practiced, the most common construction methods involve one of the following approaches: wood frame exterior walls, concrete block or cinderblock walls, poured-in-place concrete walls and "tilt-up" pre-cast concrete walls.
The least expensive method of wall construction is the wood frame exterior wall method which is widely used in residential construction. However, it does not provide a very strong facade, as is particularly evident when the exterior and interior sheathing have not been attached to the frame, Moreover, wood frame construction is particularly notorious for its susceptibility to fire, termites, warping, water damage and rot, and the use of wood in construction has caused extensive depletion of our natural forests. Furthermore, unless the spacings between the wood studs are completely filled with thermal insulation, wood frame exterior walls provide poor insulation from heat and cold.
As an alternative to wood frame structures, concrete block construction offers some improvements, particularly its strength, but suffers two principal disadvantages. First, concrete block construction is significantly more expensive than wood frame construction. The higher costs arise from the materials themselves, as well as from the labor required in handling the blocks, e.g., the transporting and hand setting of the blocks, etc.
Secondly, concrete blocks provide very poor thermal insulation. For example, since common concrete blocks include a concrete "webbing" between the inner and outer surfaces of the block, relatively short thermally conductive paths exist between the two surfaces, which make the blocks poor thermal insulators. Therefore, a solid sheet of right insulation must be bonded to any wall formed of the blocks in order to provide adequate thermal insulation. This involves additional labor and material costs and, since the commonly used insulation (polystyrene or urethane foam) is flammable and produces toxic fumes upon combustion, it also involves a fire hazard as well. This hazard can, of course, be mitigated by bonding the insulation between two walls of concrete blocks, but such double-walled construction involves totally intolerable cost levels.
Similarly, wall sections made from product-in-place concrete are also expensive, since extensive forms must be set in place and the concrete pumped upwardly against gravity or otherwise delivered to the "pour" site. Furthermore, the inner and outer forms are usually held together by metal ties, or "snap ties", which leave surface imperfections on the concrete, that must be hand-smoothed after the forms are removed. In addition, after the forms are disassembled, they can only be reused if first treated with an oil-like substance to prevent concrete from sticking. Thus, forms are often destroyed after use, thereby ultimately adding to the waste of natural wood resources.
It can be readily appreciated, therefore, that the costs of materials and labor involved in erecting the forms are significantly greater than those of wood frame construction. In addition, the thermal insulation provided by concrete walls is about as poor as that of the concrete block and usually requires bonding a sheet of insulating material to the wall, with the same drawbacks, however, as discussed with respect to concrete block construction.
One alternative to concrete block and poured concrete wall construction has been the use of pre-fabricated concrete panels, produced at a place distant from the construction site (i.e., off-site). Aside from the costs of materials used to make the panels as well as the time-consuming fabrication techniques (including a repetition of the levelling operation), additional costs arise because the panels are made off-site by a company independent of the construction contractor so that not only must the company's reasonable profits be paid but also the costs for transporting the panels to the construction site.
Moreover, structural steel is often embedded in the concrete to provide internal reinforcing for the weight of the concrete panel to prevent damage as it is erected from its form mold, transported to the construction site and as it is lifted into place in the building. However, after the panel is installed as a wall section, much of the steel reinforcing is superfluous due to the inherent compressive strength of concrete. In addition, the joining methods commonly used in securing the panels to each other and to the foundation require additional operations to prevent any structural weaknesses. Such panel fabrication suffers the same thermal insulation drawbacks as the poured concrete or concrete block methods of construction.
Recently, however multi-layer pre-fabricated concrete panels have been made, such as disclosed in U.S. Pat. Nos. 3,295,278 and 3,220,151, which include a heat insulating layer sandwiched between two layers of concrete. Such panels provide good overall thermal insulation but usually include steel reinforcing rods or concrete dowels between the inner and outer layers, causing short thermal paths between layers, which generate "cold spots" in the panels. In addition, no method of fabrication has heretofore been developed to lessen the costs still associated with forming pre-fabricated concrete panels. Moreover, no method of fabrication has been developed for enabling convenient and inexpensive on-site fabrication of multi-layer structural panels.
It is therefore an object of the present invention to provide a new and improved form means for construction. Another object of the present invention is to provide a new and improved form means for use in construction, to provide strong and thermally insulative walls, at relatively low costs.
It is another object of the present invention to provide a new and improved form means for forming pre-cast structural panels directly at the construction site.
It is a further object of the present invention to provide a new and improved apparatus for making pre-cast structural panels which can be installed in place without requiring much reinforcing structural steel heretofore used in such panels.
It is another object of the present invention to provide a new and improved form means for forming pre-cast structural panels, which can obviate the need for pre-stressing the reinforcing structural steel in such panels as heretofore done.
It is also an object of the present invention to provide a new and improved form means for making pre-cast structural panels, which substantially eliminates the waste of plywood or other form structures.
It is an additional object of the present invention to provide a new and improved mold form, which is inexpensive and essentially completely re-usable.
It is also another object of the present invention to provide a new and improved form means for forming pre-cast structural panels, which substantially eliminates the need for hand finishing the surfaces of the panels.
It is still a further object of the present invention to provide a new and improved apparatus for making pre-cast concrete panels for use in wall construction, which enables substantial thermal insulation to be provided in the panels without requiring double-walled construction or otherwise significantly raising construction costs.
It is also a further object of the present invention to provide a new and improved form means for forming pre-cast structural panels which enables substantial flexibility in panel design, size and characteristics by the same basic form means.
It is also an additional object of the present invention to provide a new and improved form means, which eliminate the need for multiple form erection and disassembly and allows concrete to be poured directly from a transit truck or a mixer.
It is still another object of the present invention to provide a new and improved form means, which enables the inexpensive fabrication of curved wall sections by essentially the same basic form means.
Objects and advantages of the invention are set forth in part herein and in part will be appreciated herefrom, or may be learned by practice with the invention, the same being realized and attained by the apparatus set forth in the appended claims. Accordingly, the present invention resides in the novel structures and apparatus disclosed and claimed herein.